1. Field of the Invention
THIS INVENTION relates to well-cleaning systems.
2. Prior Art
AU-B-39856/93 (655111) (McCASKER) disclose a well-cleaning system particularly suitable for cleaning sewerage pump-station wells.
A common and expensive problem in most sewerage systems is the build-up of fatty residues on the walls and components of sewerage holding wells. If not regularly removed, these residues will adversely affect the efficiency of the sewerage system, causing damage to the expensive pumps and creating an unhealthy and smelly environment.
The well-cleaning system disclosed in AU-B-39856/93 discloses a rotary spray device mounted on a pivoting arm. Mains water is delivered to the device by a solenoid valve. The water travels through the two spray arms to special nozzles which are directed at the well's walls and components. The nozzle mountings are manually adjustable so that the water can be directed to “hard to get at” corners, and the speed of rotation is also manually adjustable. The solenoid valve is operable by a relay in the control board of the well's pump, so that it opens when the pump turns on. Thus, the cleaning process proceeds as the sewage level is dropping. The solenoid closes when the pump stops and so water consumption is kept to a minimum. The mounting bracket allows the washer to pivot back against the wall to allow uninhibited access to the pump(s) and other equipment at the base of the well.
While the well-cleaning systems hereinbefore described have found ready acceptance with civic and public authorities (eg., in Australia) responsible for handling sewage, a number of potential areas for improvement of the systems have been identified.
In some installations, it has been found that frequent well pump-out cycles result in large volumes of water being sprayed into the wells. Not only is this unacceptable from a water conservation aspect, but the water adds to the volume of sewage which must be treated at the sewerage treatment facility.
In normal operation the system only uses water to perform its cleaning function in the well. Wells can often be a source of bad odours and/or corrosive gases. It would be advantageous to inject into the water (a) a deodorant mask to overcome, or minimise, the odours and/or (b) chemical and/or biological additives to improve the quality of well contents.
Hydrogen sulphide (H2S) gas is a major problem in sewage. It is toxic, explosive, corrosive and has an extremely offensive odour. It would be advantageous to provide a gas detector in the well to measure the H2S gas concentrations, to connect such a detector to a control unit which can operate the well-cleaning system when a predetermined H2S gas concentration is reached.
As the pumping-station wells are often located at locations remote from the control centre for the sewerage system, eg., for a city or local government area, it would be advantageous if the well-cleaning system could communicate conditions in the well to the control centre and be controlled therefrom in response to the conditions communicated.
In many countries, including the USA, the work-safety requirements for the man-entry of wells is extremely rigorous, and so man-entry is to be avoided, if possible, for the installation, maintenance, repair or replacement of equipment, eg., pumps, in the wells. It would be advantageous if the well-cleaning system could be installed, or retrieved, without requiring man-entry to the well. It would be further advantageous if the mounting for the well-cleaning system could take advantage of existing equipment installed in the well.
Finally, in some countries, eg., the United Kingdom, the use of reduced pressure zone (RPZ) valves, to prevent the backflow of water from the well-cleaning system to the reticulated mains water supply is not permitted. It is, therefore, necessary to provide a pressurised water supply, for well-cleaning system, which is isolated by an air gap from the mains supply.